Most of the contemporary electrically driven motor vehicles are designs which have been standardized with an internal-combustion machine as the power pack. As the internal-combustion engine runs best at an optimum rpm, and structurally has to be in a cubic form, the need to have gears and a lot other mechanical parts is always there.
While switching over to an electric-drive principle to run a motor vehicle, the first efforts had been to replace the internal-combustion engine with a high-rpm electric motor. But then there was this need to have a sizeable number of accumulators which, of course, would weigh down the vehicle considerably. It was difficult to create extra space for the accumulators; and changing the batteries in case of emergencies was cumbersome. Additionally, there had been a trend in the recent past to go for small-wheeled vehicles to reduce physical size and to increase maneuverability. This tended to increase the rolling friction between the wheels and the road surface, as the ratio between the chord which forms at the road contact and the circumference of the tire increases with increasingly smaller wheels. It is a major drawback for electric-vehicle design; reducing the range of the vehicle for a full battery charge.
There had been designs in the past which utilized an electric motor inside the wheel. On many occasions the wheel is turned into a wheel motor. But as there are no gears in the case of a direct-driven wheel motor, in order to generate high torques, either the diameter or the thickness of the wheels have to be increased: This makes the wheels heavy. To hold together those wheels, the axles and the chassis (or the shell) all have to be stronger and thus would be heavier than in a vehicle driven by a centrally located power pack.
How to do away with the numerous mechanical parts that weigh down an electric motor vehicle? And how to reduce the rolling friction to reduce the cruising power requirement of an electric motor vehicle? These were the two major pointers leading to this invention.